DESCRIPTION (Adapted from applicant abstract): Host defenses against C. immitis are mediated by specifically sensitized T cells. In the mouse model, both genetically susceptible (BALB/c) and genetically resistant (DBA/2) mice mount cell-mediated immunity (CMI), as measured by delayed- type hypersensitivity (DTH), by day 9 of infection. Thereafter, responses of these mouse strains diverge. Whereas DTH persists in DBA/2 mice, BALB/c mice become anergic. Dr. Mitchell has found that these differences extend into the types of cytokines produced during active disease. DBA/2 mice produce IFN- earlier in infection and at higher levels than BALB/c mice; conversely, BALB/c mice produce IL-4 earlier and at higher levels than DBA/2 mice. The importance of these cytokines, as determinants of host response to disease, was established by showing that protection is potentiated in BALB/c mice by either treatment with recombinant IFN- , recombinant IL-12, or by in vivo depletion of IL-4. Similarly, in resistant DBA/2 mice, in vivo depletion of IFN- exacerbated disease. Taken together, these data provide evidence that the preferential induction of these immunomodulatory cytokines may have profound effects on the course of disease. Two specific aims are proposed. The first aim will be to delineate the kinetics and magnitude of cytokine expression in BALB/c and DBA/2 mice challenged by the pulmonary and systemic routes. Cytokine-specific mRNA will be measured by reverse-transcription polymerase chain reaction (RT- PCR) of RNA isolated from tissues and from unfractionated cells and purified cell populations from lungs, spleen, liver, and lymph nodes. Production of cytokine protein will be quantified by enzyme-linked immunosorbent assays (ELISA) of homogenates prepared from these tissues. The second aim will be to assess the biological relevance of individual cytokines on the host response by in vivo depletion of cytokines with neutralizing anti-cytokine antibodies. The effects of these interventions will be assessed by determining fungal load and cytokine modulation at the molecular and protein levels in tissues. Dr. Magee argues that completion of these aims will delineate new and fundamentally important aspects of mechanisms of host defenses in coccidioidomycosis and have significant implications for immunotherapeutic intervention in this disease.